An Amtrak spokesman says more than 500 passengers are aboard the trains - The Southwest Chief from Los Angeles, the Illinois Zephyr from Quincy and the California Zephyr from the San Francisco Bay area.

The trains were halted late Monday near Mendota, about 80 miles west of Chicago.

Amtrak says the trains are operating on tracks owned by the BNSF railroad. He says BNSF employees are working to reopen the tracks to get the trains moving.

The rail service's spokesman says passengers will remain on the trains and are being fed and kept comfortable by the crew. He says Amtrak officials are in contact with emergency responders in the event passengers encounter problems.

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